Answer:
Friction produces heat because it causes the molecules on rubbing surfaces to move faster and have more energy.
Explanation:
Science 
 
        
                    
             
        
        
        
My guess would be mRNA or RNA but I'm not too sure about this question, sorry. 
 
        
             
        
        
        
Hello there! 
Your answer should be ATP is a stored form of energy.
You see, Think of it as the “energy currency” of the cell. If a cell needs to spend energy to accomplish a task, the ATP molecule splits off one of its three phosphates, becoming ADP (Adenosine di-phosphate) + phosphate. The energy holding that phosphate molecule is now released and available to do work for the cell. Hope this works!
 
        
             
        
        
        
the chemical bonds were broken when they were digested and the chemical composition of the food was changed